| 摘要 |
PURPOSE:To obtain a ball unit of high sphericity while continuing a workpiece to be properly held and facilitated in its setting to a proper position by providing a movement preventing surface, which prevents the workpiece from moving in the radial direction of a driving lap, in a float in its upper end part. CONSTITUTION:While a spherical workpiece 3 is held is magnetic fluid 7, containing an abrasive grain, by a driving lap 1, float 5 receiving levitating force by a magnetic field formed by a magnet 6 and the internal peripheral surface of a guide ring 4, the workpiece 3 is polished by rotating the driving lap 1. Here the flat 5 forms in its upper end part a movement preventing surface 8 for preventing the workpiece 3 from moving in the axial direction of the driving lap 1. As a result, the workpiece 3 can be easily arranged along this movement preventing surface 8 in a peripheral edge part of the flat 5, and setting the driving lap 1 from the upper enabling the workpiece 3 to be surely held to a proper position, a ball unit of high sphericity can be obtained by preventing movement of the workpiece 3, when it is polished, by rotating the driving lap 1. |
